FIG. 16 is a top view of conventional optical reflection device 501. Optical reflection device 501 includes polygon mirror 11 having a polygonal shape. Rotating about rotation axis 11A, polygon mirror 11 reflects a laser beam emitted from laser emitter 12 on reflection surface 11B, sweeping the laser beam on scanning surface 13 of a photosensitive drum of a laser printer.
This type of conventional optical reflection device is disclosed in Patent JP11-281908.
Polygon mirror 11 having the polygonal shape has a certain thickness from the rotation axis, hence preventing optical reflection device 501 from having a small size.